1, the so-called fixed-focus lens. 50mm 50mm is a scalar data, which simply reveals the optical structure of the lens and tells the user the hard indicators of the lens, such as how wide the field of view is, whether it can be zoomed, and so on. A fixed-focus lens is like your eyes. It is impossible to enlarge or narrow the observed person while keeping the distance between the observer and the observed person unchanged. It can also be said that the zoom lens that narrows or expands the field of view is only because it can zoom. That is to say, the so-called 50-0 or 0-50 does not exist when the distance between the observed person and the observer is constant, and the shortest focal length of super wide angle is only 6mm2, so-called telephoto lens. 18-200mm The lens with high zoom 18-200mm you mentioned is worse in imaging than the small zoom lens with the same work. The specific indexes such as dispersion, large aperture sharpness and backlight performance are weaker than them, and the zoom ratio is 1 1. Objectively speaking, this kind of lens is usually used to cope with complex shooting conditions and travel lightly. Speaking of Canon Xiaobai, in fact, a large part of its price is also divided into manufacturing processes, such as waterproof performance, metal mirror body, excellent lens structure, other lens processes/materials, and research and development funds. You know that if you buy his lens at a high price, it is equivalent to supporting his continued development, as well as research expenses and so on. The two versions of this lens are is and non-IS. 18-200 How does the lens feel? Is the focusing speed fast? Is the aperture constant? How big is the aperture? We should know that the manufacturing cost of large aperture lens is exponentially increasing, for example, 50MM F 1.8 is 650, 50MM F 1.4 is 2400, and 50mm f 1.2L is 1 10,000. The same focal length, different aperture index, the price difference is very big. Xiaobai sacrificed the convenience of a large zoom ratio and used a small zoom ratio of 70-200 to get more. It is worthwhile for a demanding enthusiast and professional photographer to have high image quality and enjoy the performance of large aperture for users at a suitable price. 3. 100mm The first is a fixed-focus lens. Simply put, it is called 100 mm fixed focus, but because this lens has super macro optical performance and high magnification, it is simply called "Budweiser". Intuitively speaking, it is to put the object you want to shoot in a large size and show you a picture of Budweiser:

Your 50mm also has a special 50mm macro version, which is now called "50 micro". By analogy, when it comes to zoom lenses with macro, the magnification is generally not high (except DC), so no one will name the zoom lens with macro as subjective, but it has spread and everyone calls it that. Finally, the data you mentioned are actually important information to understand the working performance and principle of a camera. For professionals or enthusiasts, it is necessary to know a camera. It allows you to combine with the camera and shoot with ease. Generally speaking, in the digital age, it is spread on the display, and there is a certain post-technology, so the lens effect of more than 3000 yuan is very good. In terms of color, the color effect brought by lens coating is not the same. There are also differences in the SLR camera itself, such as differences in coloring, excluding the influence of color temperature. For example, the default color of some cameras is yellow, some cameras are purple, some cameras are green, and there are anti-mania, high ISO color reproduction, resolution and dynamic range of sensors. Knowing more will be good for shooting. If you still don't understand, you can ask me QQ 2872 1473.